After business school, David Velez moved to Latin America to become a venture capitalist. But after finding a dearth of startups to invest in, he founded one of his own. Since then, Nubank has grown into the largest independent digital bank in the world. The Brazil-based company has over 39 million users and a valuation north of $25 billion. David shares how Nubank built a waitlist of over a million people in just 18 months, why the company's first product was a purple credit card, and how waking up at 5am every day makes him a better founder.